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Linux Kernel Selftests

The kernel contains a set of "self tests" under the tools/testing/selftests/ directory. These are intended to be small tests to exercise individual code paths in the kernel. Tests are intended to be run after building, installing and booting a kernel.

On some systems, hot-plug tests could hang forever waiting for cpu and memory to be ready to be offlined. A special hot-plug target is created to run full range of hot-plug tests. In default mode, hot-plug tests run in safe mode with a limited scope. In limited mode, cpu-hotplug test is run on a single cpu as opposed to all hotplug capable cpus, and memory hotplug test is run on 2% of hotplug capable memory instead of 10%.

Running the selftests (hotplug tests are run in limited mode)

To build the tests:

$ make -C tools/testing/selftests

To run the tests:

$ make -C tools/testing/selftests run_tests

To build and run the tests with a single command, use:

$ make kselftest

Note that some tests will require root privileges.

Build and run from user specific object directory (make O=dir):

$ make O=/tmp/kselftest kselftest

Build and run KBUILD_OUTPUT directory (make KBUILD_OUTPUT=):

$ make KBUILD_OUTPUT=/tmp/kselftest kselftest

The above commands run the tests and print pass/fail summary to make it easier to understand the test results. Please find the detailed individual test results for each test in /tmp/testname file(s).

Running a subset of selftests

You can use the "TARGETS" variable on the make command line to specify single test to run, or a list of tests to run.

To run only tests targeted for a single subsystem:

$ make -C tools/testing/selftests TARGETS=ptrace run_tests

You can specify multiple tests to build and run:

$  make TARGETS="size timers" kselftest

Build and run from user specific object directory (make O=dir):

$ make O=/tmp/kselftest TARGETS="size timers" kselftest

Build and run KBUILD_OUTPUT directory (make KBUILD_OUTPUT=):

$ make KBUILD_OUTPUT=/tmp/kselftest TARGETS="size timers" kselftest

The above commands run the tests and print pass/fail summary to make it easier to understand the test results. Please find the detailed individual test results for each test in /tmp/testname file(s).

See the top-level tools/testing/selftests/Makefile for the list of all possible targets.

Running the full range hotplug selftests

To build the hotplug tests:

$ make -C tools/testing/selftests hotplug

To run the hotplug tests:

$ make -C tools/testing/selftests run_hotplug

Note that some tests will require root privileges.

Install selftests

You can use kselftest_install.sh tool installs selftests in default location which is tools/testing/selftests/kselftest or a user specified location.

To install selftests in default location:

$ cd tools/testing/selftests
$ ./kselftest_install.sh

To install selftests in a user specified location:

$ cd tools/testing/selftests
$ ./kselftest_install.sh install_dir

Running installed selftests

Kselftest install as well as the Kselftest tarball provide a script named "run_kselftest.sh" to run the tests.

You can simply do the following to run the installed Kselftests. Please note some tests will require root privileges:

$ cd kselftest
$ ./run_kselftest.sh

Contributing new tests

In general, the rules for selftests are

  • Do as much as you can if you're not root;
  • Don't take too long;
  • Don't break the build on any architecture, and
  • Don't cause the top-level "make run_tests" to fail if your feature is unconfigured.

Contributing new tests (details)

  • Use TEST_GEN_XXX if such binaries or files are generated during compiling.

    TEST_PROGS, TEST_GEN_PROGS mean it is the executable tested by default.

    TEST_CUSTOM_PROGS should be used by tests that require custom build rule and prevent common build rule use.

    TEST_PROGS are for test shell scripts. Please ensure shell script has its exec bit set. Otherwise, lib.mk run_tests will generate a warning.

    TEST_CUSTOM_PROGS and TEST_PROGS will be run by common run_tests.

    TEST_PROGS_EXTENDED, TEST_GEN_PROGS_EXTENDED mean it is the executable which is not tested by default. TEST_FILES, TEST_GEN_FILES mean it is the file which is used by test.

Test Harness

The kselftest_harness.h file contains useful helpers to build tests. The tests from tools/testing/selftests/seccomp/seccomp_bpf.c can be used as example.

Example

.. kernel-doc:: tools/testing/selftests/kselftest_harness.h
    :doc: example

Helpers

.. kernel-doc:: tools/testing/selftests/kselftest_harness.h
    :functions: TH_LOG TEST TEST_SIGNAL FIXTURE FIXTURE_DATA FIXTURE_SETUP
                FIXTURE_TEARDOWN TEST_F TEST_HARNESS_MAIN

Operators

.. kernel-doc:: tools/testing/selftests/kselftest_harness.h
    :doc: operators


.. kernel-doc:: tools/testing/selftests/kselftest_harness.h
    :functions: ASSERT_EQ ASSERT_NE ASSERT_LT ASSERT_LE ASSERT_GT ASSERT_GE
                ASSERT_NULL ASSERT_TRUE ASSERT_NULL ASSERT_TRUE ASSERT_FALSE
                ASSERT_STREQ ASSERT_STRNE EXPECT_EQ EXPECT_NE EXPECT_LT
                EXPECT_LE EXPECT_GT EXPECT_GE EXPECT_NULL EXPECT_TRUE
                EXPECT_FALSE EXPECT_STREQ EXPECT_STRNE